Process for purification of tobacco smoke



United States Patent O 3,298,380 PROCESS FOR PURIFICATION OF TOBACCOSMOKE Eldon E. Stahly, Pompano Beach, Fla., assignor to Oliver W. Burke,Jr.,' Fort Lauderdale, Fla. N Drawing. Filed Dec. 14, 1962, Ser. No.244,572

1 Claim. (Cl. 131-462) of nickel carbonyl per pack of filteredcigarettes. On the basis of their studies, cumulative exposure to thesequantities of nickel was suggested by the Drs. Sunderman to be in abroader sense the term metal carbonyl also includes v the analogousmetal nitrosyl carbonyls and the metal hydrocarbonyls, which are similarcompounds in which one of the carbonyl groups has been replaced by anitrosyl or a hydrocarbonyl group, and except where the contextindicates to the contrary, the term is employed in said broader senseherein.

Objects of the invention, severally and interdependently, are to providean improved cigarette having a sub stantially reduced content of metalcarbonyls in its smoke output as compared to conventional plain orfilter-tipped cigarettes; to provide a process for the purification oftobacco smoke by removing metal carbonyls therefrom by converting thesame to non-volatile materials; to provide an improved cigarette smokefrom which metal carbonyls are substantially eliminated; to provide animproved method in which volatile metal carbonyls present in tobaccosmoke in small amounts are converted to nonvolatile materials in amanner which etfectively prevents their leaving a cigarette in thesmoke; and to provide an improved method in which a ligand material isreacted withvolatile metal compounds in the tobacco smoke and convertsthem into non-volatile compounds.

Other objects and advantages of the invention, and of preferredembodiments thereof, will be apparent from the following-description andfrom the illustrative examples appended thereto. 1

The invention resides in the new and useful methods and products hereindisclosed, and is more particularly defined in the appended claim.

GENERAL DESCRIPTION Conventional tobacco smoke, more particularlyconventional cigarette smoke, contains substantial traces of metalcarbonyls, and especially of nickel, cobalt and iron carbonyls, and suchmaterials are reported to be toxic and carcinogenic to animals.

Thus, it has been reported in a paper by the Drs. F..W. Sunderman (Sr.and Jr.), based on tests of six different brands of cigarettes, thatnickel carbonyl containing from 0.4 to 0.6 microgram nickel percigarette (corresponding to about 20% of the total nickel of thetobacco) passes through the butt and filter of conventional plain orfilter cigarettes, reaching the smoker (Medical Science, page 617, May25, 1961; American Journal of Clinical Pathology, 35, 203 (1961)). Instudies with rats, small amounts of nickel carbonyl were found by theDrs. Sunderman to be carcinogenic. The nickel delivered in the smokedrawn from the butt ends of the cigarettes amounted to up to 8micrograms nickel per pack of 20, or 23.5 micrograms nickel carbonyl perpack of 20 of unfiltered cigarettes; and up to '12 micrograms nickel or35 micrograms a possible cause of the so-called smokers pulmonarycancer. Based on the reported figures, a person who smokes a pack ofcigarettes per day over a period of a year subjects himself to about oneand one-half times the amount of nickel required to induce pulmonarycancer in rats, which are considered to be notably resistant topulmonary cancer.

Aside from the nickel carbonyl reported, I have found that traces ofvolatile cobalt and iron compounds are also present, apparently ascarbonyls, in cigarette smoke. The cobalt is present in somewhat smalleramounts than the nickel, about 1.3 micrograms of cobalt passing thefilters per pack of filter cigarettes; and thte iron is present in abouttwice the amount of nickel in the smoke of some brands of cigarettes.

Aside from the carcinogenic aspects of metal carbonyls reported by theDrs. Sunderman, it has long been known that such compounds are highlytoxic and dangerous materials even in trace amounts. Thus Sax, Handbookof Dangerous Materials, published in 1951 by Reinhold PublishingCompany, New York, prescribed a maximum allowable concentration ofcobalt in the air as 0.4 part per million, and the Twenty-SecondAmerican Conference of Government Hygienists in April 1960 placed themaximal atmospheric concentration of nickel carbonyl for a working dayat 1 part per billion (AMA. Arch. Environmental Health 1, 140-144, year1960). Iron carbonyl is also considered to be toxic, although less toxicthan nickel and cobalt carbonyls. Accordingly, the cumulative toxicityeffects of these three metal carbonyls in tobacco smoke can be expectedto be greater than that reported for nickel carbonyl alone.

Likewise, aforesaid Drs. Sunderman in the above cited paper,demonstrated that cigars and pipe tobacco contain nickel in amountssimilar to cigarette tobaccos, and similar amounts of nickel carbonylper gram of tobacco tobacco, 6 micrograms cobalt per gram of tobacco andover 400 micrograms iron per gram of tobacco, and that over a microgramof each metal per gram of tobacco smoked can reach the smoker inconventional methods of smoking.

Hence it is evident that the quantities of metal carbonyls present inthe smoke from conventional plain and 5 from such smoking articles isbased on the removal of metal carbonyls from the tobacco smoke by theformation of non-volatile complexes by combination of the metalcarbonyls with a ligand, which for the purpose of this invention is anitrogenous organic compound free of phosphorus, that acts as acomplexing agent which forms com- '9 (D plexes of low volatility withtransition metal carbonyl compounds in the presence of otherconstituents of to bacco smoke, more particularly in the presence ofmoist carbon dioxide. The practice of my invention does not depend onthe formation of exact empirical complexes since mixtures of suchcomplexes may be formed with equal benefit for my process.

Thus volatile metal compounds in the cigarette smoke by the presentinvention are converted to non-volatile complexes by contacting thesmoke with one or more ligand organo-nitrogen compounds as abovedefined. These compounds maybe hydrocarbon or hydrocarbonoxy substitutedcompounds of nitrogen. Especially suitable as ligands in the presentinvention are (A) the amide compound ligands which comprise (1) acidamides, namely primary, secondary and tertiary acid amides, the mono-N-substituted primary and secondary acid amides and the di-N-substitutedprimary acid amides, (2) the diamides namely urea and the N-substitutedureas and (3) diacidamides, and (B) the nitrile compound ligands whichcomprise (1) nitriles; (2) isonitriles and (3) cyanoamides.

' The acid amide ligands (A above) are represented by the formulae:

RCONR'R RRNCONR R RCONRCONR RCOR and the nitrile type ligands (B above)by the formulae;

RCN; RNC; RR'NCN; wherein R, R, and R and R may be the same or differentradicals selected from the group consisting of hydrogen, andunsubstituted, hydroxysubstituted, and amino substituted alkyl, alkenyl,alkynyl, cycloalkyl, aryl, alkaryl, aralkyl, alkoxyaryl, terpenyl,pyridyl, alkylpyridyl, pyridylalkyl, pyrrolidinyl quinolyl, etc.radicals, and wherein the aforesaid radicals of the compound cannot allbe hydrogen simultaneously and wherein R is selected from the groupcomprising piperidyl, alkylpiperidyl, pyrrolidinyl, piperazinyl,morpholinyl and like radicals, the linkage to the CO group being via thering nitrogen atom of R The restriction placed on R, R, R and R isrequired because of the low volatility requirements for use in filtersfor tobacco smoke. As indicated it has been found that R, R, R R and Rof the above formulae can have amino substituents. Although the aminogroup may be inactivated by carbon dioxide of the tobacco smoke, theamide moiety can still afford ligand activity for complexing transitionmetal carbonyls. The amino-C H CONH is an effective ligand of myinvention. Ligands containing from 8 to 24 or more carbon atoms arepreferred.

The complexes are formed by passing the smoke containing the metalcarbonyls into contact with one or more of said ligands or over orthrough a filter material acting as a carrier body for the ligandmaterial, and preferably comprising fibrous material, for example,cellulose acetate tow, prepared with the ligand therein or wholly orpartly coated with the ligand or with material such as activated carboncarrying the same.

In the practice of my invention for example in making tobacco smokefilters one or more of the ligands or complex-forming compounds orcomponents with or without a solvent or plasticizer are preferablydispersed on solid adsorbents; for example, the liquid orcomplex-forming components may be vaporized onto an adsorbent material,or a solution of a ligand may be applied to adsorbent material such ascarbon, e.g., activated carbon, silica, pumice, vermiculite, clay,asbestos, polyesters, polystyrene, and cellulosic materials, e.g.cotton, cellulose, cellulose acetate, cellulose acetate-butyrate,cellulose propionate, tobacco, and other absorbing materials having ahigh surface area per unit weight or per unit volume.

The ligand material of the present invention may be incorporated in orwith the smoke-permeable bases, carriers or filters which themselves mayembody various adhesives, adsorbents and surface area augmentingmaterials, and such incorporation of ligand material also may be madeduring the manufacture of the filter ma terial or'filters and'thus suchligand materials can be in"- corporated with the materials and duringthe processes as disclosed, for example, in US. patents as follows:

Types of ligands useful in my present invention and typical complexesbelieved to be formed thereby from transition metal carbonyls areexemplified by the following in which x=1 or 2.

Ligand (Y) Typical complex CNR Ni(CO) (Y) RCN Fe(CO) (Y) RRNCNNi(NO)(CO) (Y) RCONR'R Co(CO) (Y) RR'NCONR R Co (CO) (Y) Likewise, theligands employed herein form non-volatile complexes with other metalcarbonyls, such as:

While carbonyls such as Fe (CO) and Fe (CO) are not volatile at roomtemperature they decompose giving volatile Fe(CO) at temperatures of C.and higher. Heating above 100 C. aids in the formation of thenonvolatile complexes, particularly with iron carbonyls. The heat of thetobacco smoke which contributes to the formation of the volatile ironcarbonyl thus also aides in the rate of formation of the complexes inthe cigarette filters of the present invention.

Vapor pressure observed for representative metal carbonyls andindicatlve of the volatility thereof are:

' Ni(CO) 134 mm. Hg at 0 C.;

238 mm. Hg at 15 C.

Co(CO) COH 760 mm. ca. 10 C. C0(NO)(CO) 91mm. at 20 C. Co (CO) 0.72 mm.at 16 C. Fe(COH) (CO) 11 mm. at -10 C. Fe(CO) 26 mm. at 16 C. Fe(CO)(NO) 760 mm. at C.

The alkyl groups preferred as R substituents (which term severallyincludes R, R, R and R in the organonitrogen ligand are the alkylscontaining not more than 24 carbon atoms (i.e., methyl to stearyl). Bothprimary and secondary alkyls, straight chain and branched chain alkylgroups may serve as R in the ligand.

Alkenyl groups preferred as R in the ligands are vinyl, .allyl, butenyl,etc., up to alkenyl groups containing not more than 24 carbon atoms.

Alkynyl R groups .of the alkynyl ligands are exemplified by propargyl,butynyl, pentynyl, hexynyl, heptynyl, octynyl, etc., up to thosecontaining preferably not more than 24 carbon atoms.

Cycloalkyl R groups of the cycloalkyl ligands are exemplified by cyclo-C-C -C c-yclododeoyl and the like cycloalkyls, ac-tetrahydro-naphthyl,decahydronaphthyl,

mono and dioctylbenzyl.

contains .not more than 24 carbon atoms and may be phenyl, naphthyl,ar-tetra-hydronaphthyl, alkoxy or alkyl phenyl, alkoxy or alkylnaphthyl, or alkoxy or algyl substituted ar-tetra-hydronaphthyl.Finally, R may be an arylene compound.

The aralkyl substituents R in the ligand which are useful in the presentinvention may be unsubstituted or hydrocarbon substituted and range fromphenylmethyl to phenyldecyl, and from mono and dimethyl-benzyl toAralkyl and arylene groups containing not more than 24 carbon atoms arepreferred.

Advantages such as non-toxicity accrue to the use of amide-s and ofcyano .compounds of carbohydrates such as the cyanoethylated derivativeof cellulose, sugars, starch, dextrin, .and the like as complexingagents, particularly when softened by a plasticizer or solvate.

If the ligand material is water-soluble then it is preferable to usea-recessed filter or a filter free of ligand material in the portioncontacting the mouth. For filters that contact the mouth non-watersoluble ligand material is preferred. In either case it is desirable touse low-volatile ligand material.

. EXAMPLES The invention as above disclosed will be more fullyunderstood by reference to the following examples which are to be takenas illustrative and not restrictive of the invention, and which areconducted in three series, namely:

Series A, in which a synthetic gas mixture of volatile metal carbonyland carbon monoxide was prepared containing small quantities upward of100 parts per million of the metal carbonyl (at least equal to themaximum proportion thereof in tobacco smoke), and in which the abilityof typical organo-nitrogen ligand materials to extract such traces fromthe diluent gas was established.

Series B, in which the same synthetic metal carbonyl gas mixtures wereemployed to test the eflicacy of typical organo-nitrogen ligands of thisinvention in single pass cigarette filters.

1 Series C, in which the synthetic metal carbonyl gas mixtures werereplaced by tobacco smoke and the advantage of the invention in reducingthe metal carbonyl contact .of such smoke was demonstrated.

For the series A and series B example, metal carbonyls were prepared, orobtained commercially, and put into a gas stream from which they weresubsequently removed by the ligand materials employed in the presentinvention. These tests were followed by the Series C actual cigarettesmoking tests wherein ligands were employed as filter components.

Series A Example 1 (Cntr0l)..Nickel tetracarbonyl was generated bypassing carbon monoxide of 98% purity from a cylinder over 3.75 gramsRaney nickel (2.625 g. Ni on bing solution. Two simple tests were usedto demonstrate the presence of the nickel tetracarbonyl in the gas: (1)

the flame of the burner displayed a grey luminosity when the nickelcarbonyl was present in an amount as low as 1 p.p.m. and (2) pinpointheating of the glass outlet from the generator deposited a spot nickeldeposit or mirror on the wall of the glass tube. As litle as 10 mole ofnickel tetracarbonyl gave an observable metallic nickel deposit in thistest, and thus was used as a sensitive test. Also, the weight of amirror formed in a small glass tube served to establish the metalcarbonyl content of a measured quantity of gas.

When the gas at 200 cc./minute was shown to contain at least p.p.m. ofnickel tetracarbonyl (by mirror test) Example 2 was carried out. Theflame of the burner showed a strong grey color in this range ofconcentration of nickel tetracarbonyl. This test demonstrated that thescrubbing apparatus itself did not decompose the nickel carbonyl, anddid not remove the nickel carbonyl from the gas.

Example 2 (Control) .-100 ml. of benzene was placed in the scrubber ofExample 1 and the gas rate from the nickel tetracarbonyl generator washeld at 200 cc./ minute. Appreciable removal of nickel tetracarbonyl wasnot observed either by mirror test or change in intensity of the greycolor after about 10 minutes of passing the gas through the scrubber.This example demonstrated that a solvent alone in the absence of aligand does not remove the nickel carbonyls from the gas stream to aneffective degree because of the appreciable partial pressure of thenickel carbonyl in the solution.

Example 3.A solution of 10% stearic amide in benzene was substituted forthe benzene of Example 2 with complete removal (by mirror deposit test)of the nickel carbonyl from the gas stream.

Example 4 .--A mixture of cobalt tetracarbonyl hydride and cobalttetracarbonyl was generated according to the precedure of Gilmont andBlanchard (Inorganic Syntheses, vol. II, pp. 238-243, McGraw-Hill BookCo., Inc., 1946). The hydride in the glass trap was volatilized at about30 C. by passing a stream of carbon monoxide into the trap, the outletof which was attached to the fritted glass scrubber of Example 1containing a 20 wt. percent solution of hydrogenated t-allo-w acid amidein benzene. The exit gas from the scrubber contained nil cobaltcompounds by the mirror test and the flame test.

Example 5.Example 4 was repeated employing cis, trans, trans-1,5,9cyclododecatriene for the benzene in preparing the 20 wt. percent tallowacid amide solution. The exit gases showed complete removal of volatilecobalt carbonyl compounds by mirror and flame tests.

Example 6.Example 4 was repeated except that the scrubber was replacedwith an absorber tube containing about 5% stearamide on finely divideddecolorizing carbon (20 g.) (No. 1551 from General Chemical Division ofAllied Chemical Corp.) At a gas rate of '50 ml./min ute, substantiallyall of the cobalt compounds were removed from the gas.

Example 7 .Iron tetracarbonyl dihydride was prepared from ironpentacarbonyl (Antara Chemical Company) by the method of Blanchard andColeman (Inorganic Syntheses, vol. II, pp 243-4, McGraw Hill BookCompany, In-c., 1946). The trap containing the irontetracarbonyldihydride (1 gram) was allowed to warm (from 70 C.) whilepassing a stream of carbon monoxide therethrough. The carbon monoxidegas containing the small amounts of iron carbonyl and iron carbonylhydride was passed through the tube containing 0.5 g. oleic acid amideabsorbed on 20 g. Philblack 0, an iron-free carbon black (produced byPhillips Petroleum Co.). At a rate of 100 ml. gas/minute, the ironcompounds were substantially completely removed from the gas, the carbonblack absorbate after 40 minutes showing an iron content of about 0.45%(0.092 g. iron). Substitution of activated carbon for Philblack O inthis experiment gave substantially the same results.

The conclusions from the teachings of this example are that the ligandsof this invention can be employed with cigarette, cigar or pipe filterscontaining carbon, more particularly activated carbon.

Example 8.Ten grams diallylcyanamide in 100 grams benzene were placed inthe fritted glass scrubber of EX- ample 2 and Example 3 was performedusing the conditions of Example 2. Substantially complete removal of thenickel carbonyl from the gas stream was observed by the flame test.

Examples 9 and ]0.Example 8 was repeated using a solution ofisophthalodinitrile in xylene (2% solution) in the scrubber. After 10minutes the scrubber had absorbed about 0.5 milligram of nickel.Repeating the example with o-phthalonitrile gave substantially the sameresults.

SeriesB Example 11.- Cigarette filter grade cellulose acetate tow ofabout 40% acetyl content, 5 denier/single filament, 100,000 totaldenier, was used as filter material. One and one-fourth grams weresoaked in 100 g. of benzene solution containing 5 g. la-uric amide. Thematerial was dried (1.5 g.) and placed compactly in a glass tube intowhich it fit snugly over a length of 6 inches. This filter tube wasattached to the nickel carbonyl generator of Example 2. At a gas rate of30 ml./minute for 30 minutes the nickel tetracarbonyl could not bedetected in the exit gas from the tube. By spectrochemical analysis thefilters were found to contain 0.015% nickel (vs. 0.000045% before use),or a total of 224 micrograms nickel absorbed.

Example 12.Example 11 was repeated using a 6-inch length of the uncoatedcellulose acetate tow as used in Example 11. The analysis showed thatonly 10 micrograms of nickel were retained by the filter, as comparedwith 224 micrograms nickel retained by the ligand or complexing agent ofExample 11.

Example 13.Two grams niacinamide were dissolved in 48 g. isopropanol and5.07 g. of cellulose acetate tow of about 40% acetyl content (5 denierfibers) were immersed therein for minutes. The tow was drained and driedin a 70 C. oven. The dried tow showed a content of 10% niacinimide.About 0.4 g. of the tow was placed in a glass tube as in Example 11 toform a 2" long filter in the exit line from the nickel carbonylgenerator of Example 1. Passage of 400 ml. of the gas during 10 minutesshowed an adsorption of about 90 micrograms of nickel.

Example 14.--Example 13 was repeated using about 40% urea on thecellulose acetate tow in the filter. About micrograms of nickel wasadsorbed in comparison with 4 micrograms in Example 12 for a 2" lengthof uncoated tow.

Series C Example 15.-1,580 g. of cellulose acetate tow described inExample 11 was coated by immersing in an alcoholic solution of octadecylamide of acetic acid, draining and drying at about 80 C. to give afilter containing 3% of the amide. The filter material was divided into10 parts and each portion was fitted snugly into a glass-tube holder fiin diameter and was used as a back-up filter to smoke 2 filterscigarettes (Brand B) for each coated filter section. The total nickelcontent of the tobacco of these cigarettes was about 190 micrograms byspectrochemical analysis. The 10 coated filter sections after use insmoke filter were combined and analyzed for nickel content. The filtersections supplied withthe cigarettes were removed from the butts andanalyzed for nickel content. The uncoated filters showed a total nickelcontent of about 35 micrograms, and the back-up coated filters showed atotal of about 65 micrograms additional nickel content which had passedthe mamiiacturers filters Example 16.The test of Example 15 was repeatedusing uncoated cellulose acetate tow as back-up filters for Brand Bcigarettes. The total nickel adsorbed was 9 micrograms on the back-upfilter, showing the advantage of my ligand in Example 15.

Example 17.-Example 15 was repeated using cellulose acetate tow ofExample 13 coated with niacinamide to give a filter material with 10% ofthe amide. The filter material (5.5 g.) in 2-0 portions was used as abackup filter for smoking two Brand B cigarettes per portion, Le, atotal of 40 filter cigarettes (Brand B) showed a pick-up ofapproximately 1.45 microgram nickel per cigarettes (vs. 0.12 microgramin the filter supplied with the cigarette). The iron content of theback-up filter containing my ligand showed a pick-up of 78 microgramsper cigarette smoked vs. 63 micrograms per cigarette pick-up by thefilter supplied with cigarette. The cobalt absorption was 0.2 microgramper cigarette smoked for the back-up filter vs. 0.1 microgram for themaunfacturers filter.

Example 18.--A filter was preparedfrom celluose acetate tow described inExample 11 by coating with diallylcyanamide. The filter materialcontained about 13% of the cyanamide derivative. Example 17 was repeatedusing this cyanamide-coated filter instead of the niacinamide-coatedfilter. The back-up filters picked up about 1 microgram of nickel and10.4 micrograms iron per cigarette which had passed through the filtersupplied with the cigarette.

Example 19.Cellulose acetate tow (5.000 grams) of Example 11 wasimmersed in a mixture of 12 g. isopropanol, 68 g. benzene and 3 g. oleicamide for 15 minutes. The tow was drained and dried to give a filtermaterial containing 8.4% amide. The filter material was cut into 20portions of 0.273i0.005 g. each, and each portion was used in a glasstube of *7 "'I.D. as a back-up filter for smoking two Brand Bcigarettes. After smoking, the combined filters showed the followingamounts of metals absorbed per cigarette smoked:

While there have been described herein what are at present consideredpreferred embodiments of the invention, it will be obvious to thoseskilled in the art that modifications and changes may be made withoutdeparting from the essence of the invention. It is therefore to beunderstood that the exemplary embodiments are illustrative and notrestrictive to the invention, the scope of which is defined in theappended claim, and that all modifications that come within the meaningand range of equivalency of the claim are intended to be includedtherein.

I claim:

A process for the purification of tobacco smoke from a smoking articleby the removal of volatile metal compounds therefrom, which comprisespassing said smoke through a filter into the mouth of the user downstream therefrom, said filter comprising a ligand compound'containingtransition metal chelating groups, said compound being a cyanoamide.

References Cited by the Examiner UNITED STATES PATENTS 134,713 1/1873Turner 131208 2,171,986 9/1939 Poetschke 13l9 2,815,760 12/1957 Schreuset val. 131-208 2,857,249 10/ 8 Wolfe 23205 2,886,591 5/1959Lautenschlager 252-430 (Other references on following page) 9 10 UNITEDSTATES PATENTS Degering: Organic Nitrogen Compounds (1945) pub. 2 933 40 4 /19 0 Richter 131 2 3 by University Lithoprinters, YpsilantiMichigan, pp. 515 2,968,306 1/1961 Touey et a1 131208 and 51 6especially cited. 3,026,226 3/1962 Touey et a1 131208 Merck Index(Seventh Edition), pub. by Merck and FOREIGN PATENTS 5 C0., 1960, p. 8and 134 especially cited.

Mgrdichian: (Text) The Chemistry of Organic Cyano- 2 5 fi gg ggzgifi genCompounds, 1947, published by Reinhold Pub. Co., 932,560 12/1947 France.NC/C, pp- 10 and 9,664 1907 Great Britain. 10

OTHER REFERENCES SAMUEL KOREN, Primary Examiner.

Alien Property Custodian Application of Laude, Ser. MELVIN D. REIN,Examiner. No. 261,049, published May 11, 1943.

